* {
    margin: 0;
    padding: 0;
}

.block {
    width: 100%;
    height: 400px;
    border: 1px solid black;
    margin:  auto;
    position: relative;
    overflow: hidden;
    box-sizing: border-box;
}

.box_big {
    position: absolute;
    width: 100%;
    height: 400px;

}

.nav {
    transition: margin-left 0.5s linear;
}

.box {
    width: 100%;
    height: 400px;
    float: left;
}

img {
    width: 100%;
    height: 100%;
}
/*1,2,3,4,5*/
.spot {
    position: absolute;
    width: 100%;
    text-align: right;
    bottom: 5px;
}

.spot_list {

    width: 30px;
    height: 30px;
    font-size: 20px;
    text-align: center;
    border: 1px solid gray;
    border-radius: 5px;
    line-height: 30px;
    font-weight: bolder;
    margin: 10px;
    display: inline-block;
    background: rgba(255, 255, 255, 0.3);
}

.btn {
    width: 100%;
    height: 80px;
    position: absolute;
    margin: 0 auto;
    top: 160px;
}

.left_btn, .right_btn {
    width: 30px;
    height: 80px;
    z-index: 15;
    background: rgba(255, 255, 255, 0.3);
    text-align: center;
    line-height: 80px;
    border-radius: 8px;

}

.left_btn {
    float: left;
}

.right_btn {
    float: right;
}